The invention relates generally to apparatus for moving and guiding a photographic film with sprocket holes through the film gate of a scanner.
Film transport systems are known in the prior art for supporting and transporting a single film frame in a precisely controlled linear motion past a scanning aperture, e.g., of a telecine. A pin assembly carrying precision milled registration pins on a film transport carriage engages with the film sprocket holes in a path perpendicular to the film plane. After the registration pins are engaged with the sprocket holes, a precision motor pulls the single frame across the scanning aperture. When the single frame has passed by the aperture, the motor stops and the registration pins are removed from engagement with the sprocket holes in the film. The motor then returns the carriage to an initial position to engage the sprocket holes of a subsequent frame of film. (See, e.g., U.S. Pat. No. 6,081,293, entitled xe2x80x9cLinear Motion Film Gate for a Telecinexe2x80x9d
FIG. 1A shows the traditional location of the registration pins in a prior art film transport assembly of the type described above. A full fitting pin 10 and a partial fitting pin 12 provide a reference location for film perforations 14 in a film frame 16 relative to a scanning location 18, and a retrace pin 20 secures the film in place while the pins 10 and 12 are disengaged and returned to their initial position to engage a subsequent frame of film. In this configuration, the pins 10 and 12 provide linear motion of the film frame 14 while the retrace pin 20 is operative in one position only to hold the frame 14 stationary until the next movement. Typically, since the retrace pin 20 is not intended to register the film, the retrace pin 20 is located at a perforation pitch that will insure that the contacted perforation edge will not be used during image registration.
FIG. 1B illustrates a typical rectilinear motion as traced by the registration pins 10 and 12 of the prior art film transport assembly. In an advance motion 22, the registration pins move the film frame through the scanning or recording area. In a pin retract motion 24, the registration pins are withdrawn from the film perforations and in a retrace motion 26 the registration pins travel back to their initial position (while not in contact with the film). Finally, in a pin insert motion 28 the registration pins engage the film perforations of the next film frame, and the sequence is repeated.
A common problem with any film transport system of this type is that the retrace motion defines a latent period during which the film is not moved. In addition, there is time involved in the acceleration and deceleration of the pin assembly. Since the film frame has already been scanned during the advance motion, this is essentially lost or wasted time. It would be beneficial to utilize this time period for film movement, and thereby to reduce time latency in rectilinear film transport systems.
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a pin-registered device for moving and guiding a photographic film through a film gate includes four independently controllable linear members that provide two non-interfering rectilinear paths for two pairs of registration pins. More specifically, one rectilinear path is provided by a first carriage mounted for reciprocal movement parallel to a direction of film travel and a first pin assembly including a first pair of oppositely disposed pins which are engageable in oppositely disposed perforations of the film, where the first pin assembly is mounted on the first carriage for movement perpendicular to the direction of film travel for engaging and disengaging the film perforations. The second rectilinear path is provided by a second carriage mounted for reciprocal movement parallel to the direction of film travel and a second pin assembly including a second pair of oppositely disposed pins which are engageable in oppositely disposed perforations of the film, where the second pin assembly is mounted on the second carriage for movement perpendicular to the direction of film travel for engaging and disengaging the film perforations. The carriages and pin assemblies are moved and controlled such that the first pair of pins engages the perforations in the film at a start position and moves the film in the direction of film travel while the second pair of pins is repositioning to the start position for engagement with another pair of perforations. This action is then repeated to provide movement of consecutive film frames through the film gate.
The advantage of the invention is that it allows for higher pin registered film transport speeds without compromising image position stability.
These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.